1. Field of the Invention
The invention is directed toward the use of (−)-hydroxycitric acid, especially as potassium (−)-hydroxycitrate, a preferred salt of (−)-hydroxycitric acid, to reduce (“normalize”) elevated blood pressure in individuals in need thereof.
2. Description of Prior Art
Hypertension is defined as an average or sustained systolic blood pressure over 140 mm Hg and/or a diastolic blood pressure over 90 mm Hg. Hypertension has an overall incidence of 20%, with onset usually occurring after age 20. The prevalence rises with age to over 50% past age 65. Ninety-five to 99% of hypertensive individuals have essential hypertension. Persons with hypertension are three to four times more likely to experience a major cardiovascular event (e.g., myocardial infarction, cerebrovascular accident, congestive heart failure) than those without.
Essential, or primary, hypertension is often said to have no identifiable cause. However, this belies the fact that risk factors long have been identified. Hypertension is more common in African Americans at all ages and in persons from lower socioeconomic groups. Individual risk factors include family history, excessive alcohol consumption, high sodium intake, stress, sedentary lifestyle, obesity and a high intake of sugars (sucrose, fructose, glucose, etc.) Hypertension is one of the disorders which are linked to insulin resistance and elevated insulin levels. Hypertension is also linked to the excessive production of “stress hormones,” such as cortisol and corticosterone. Long-term stress is known to elevate aldosterone levels and thereby to increase sodium retention, a source of hypertension.
The various drug therapies available to treat hypertension have many drawbacks and preponderantly are unsatisfactory in cases of mild to moderate symptoms. Drug therapy is recommended for patients with sustained systolic pressure over 160 mm Hg or diastolic pressure over 100 mm Hg. Traditionally, therapy with a diuretic or beta-blocker is tried first. The dosage may be modified or an additional drug from another class may be added. Ten percent of patients may require three drugs. Diuretics—e.g., hydrochlorothiazide (Hydrodiuril; 12.5 to 50 mg/day)—have side effects which include a decreased level of potassium and increased cholesterol and glucose levels; contraindicated in patients with gout and diabetes. Potassium-sparing agents—e.g., spironolactone (Aldactazide; 25 to 100 mg/day)—have side effects which include hyperkalemia and gynecomastia.
Numerous other classes of hypotensive drugs presently are in use. Most cause a variety of undesirable effects. Alpha-blockers—e.g., doxazosin (Cardura; 1 to 20 mg/day)—have side effects which include postural hypotension and lassitude. Beta-blockers—e.g., acebutolol (Sectral; 200 to 800 mg/day)—have side effects which include congestive heart failure, bronchospasm, the masking of hypoglycemia induced by insulin, depression, insomnia and fatigue; these are contraindicated relatively in heart failure, airway disease, heart block, diabetes, and peripheral vascular disease. Alpha/beta blockers—e.g., labetalol (Normodyne; 200 to 1,200 mg/day in two doses)—have side effects which include postural hypotension and beta-blocker side effects. Centrally acting sympatholytics—e.g., methyldopa (Aldomet; 500 to 3,000 mg/day in two doses)—have side effects which include hepatic disorders, sedation and dry mouth. Peripherally acting sympatholytics—e.g., reserpine (Serpasil; 0.05 to 0.25 mg/day)—have side effects which include sedation and depression. Calcium-channel blockers—e.g., verapamil (Isoptin; 90 to 480 mg/day)—have side effects which include constipation, nausea, headache and conduction defects; these must be used with caution in heart failure or blockage. Dihydropyridines—e.g., amlodipine (Norvase; 2.5 to 10 mg/day—have side effects which include flushing, headache and ankle edema. Direct vasodilators—e.g., hydralazine (Apresoline; 50 to 400 mg/day in two doses)—have side effects which include headache, tachycardia and lupus syndrome. Angiotensin-converting enzyme (ACE) inhibitors—e.g., benazepril (Lotensin; 5 to 40 mg/day)—have side effects which include cough, rash and loss of taste; these should be used with caution in renovascular disease.
Roughly one half of all patients who are treated for hypertension stop complying with their drug treatment regimens within the first year of therapy, with many stopping within the first three months. Only an estimated 50–74% of the U.S. populace with hypertension is presently receiving treatment and, within this category of treated patients, only 50% find that their hypertension is adequately controlled by drugs. Of the drugs popularly employed, compliance rates over the long term appear to be greatest with the angiotensin-converting enzyme (ACE) inhibitors, followed in succession by the calcium-channel blockers, β-blockers and the diuretics. (Benson S, Vance-Bryan K, Raddatz J. Time to patient discontinuation of antihypertensive drugs in different classes. Am J Health Syst Pharm. Jan. 1, 2000; 57(1):51–4.) Unfortunately, β-blockers definitely increase the risk of developing diabetes Type 2, and diuretics may similarly a increase this risk. Both classes of drugs may increase insulin resistance, LDL-cholesterol and triglycerides. (Sowers J R., Bakris G. L. Antihypertensive therapy and the risk of type 2 diabetes mellitus. N Engl J Med. Mar. 30, 2000; 342(13):969–70.) (Preuss H G., Burris J F. Adverse metabolic effects of antihypertensive drugs. Implications for treatment. Drug Saf. Jun. 14, 1996; (6):355–64.)
(−)-Hydroxycitric acid (abbreviated herein as HCA) a naturally-ocurring substance found chiefly in fruits of the species of Garcinia, and several synthetic derivatives of citric acid have been investigated extensively in regard to their ability to inhibit the production of fatty acids from carbohydrates, to suppress appetite, and to inhibit weight gain. (Sullivan A C, Triscari J. Metabolic regulation as a control for lipid disorders. I. Influence of (−)-hydroxycitrrate on experimentally induced obesity in the rodent. American Journal of Clinical Nutrition 1977; 30:767.) Weight loss benefits were first ascribed to HCA, its salts and its lactone in U.S. Pat. No. 3,764,692 granted to John M. Lowenstein in 1973. The claimed mechanisms of action for HCA, most of which were originally put forth by researchers at the pharmaceutical firm of Hoffmann-La Roche, have been summarized in at least two United States Patents. In U.S. Pat. No. 5,626,849 these mechanisms are given as follows: “(−) HCA reduces the conversion of carbohydrate calories into fats. It does this by inhibiting the actions of ATP-citrate lyase, the enzyme which converts citrate into fatty acids and cholesterol in the primary pathway of fat synthesis in the body. The actions of (−) HCA increase the production and storage of glycogen (which is found in the liver, small intestine and muscles of mammals) while reducing both appetite and weight gain. (−) Hydroxycitric acid also causes calories to be burned in an energy cycle similar to thermogenesis . . . (−) HCA also increases the clearance of LDL cholesterol . . . ” U.S. Pat. No. 5,783,603 further argues that HCA serves to disinhibit the metabolic breakdown and oxidation of stored fat for fuel via its effects upon the compound malonyl CoA and that gluconeogenesis takes place as a result of this action. The position that HCA acts to unleash fatty acid oxidation by negating the effects of malonyl CoA with gluconeogenesis as a consequence (McCarty M. F. Promotion of hepatic lipid oxidation and gluconeogenesis as a strategy for appetite control. Medical Hypotheses 1994; 42:215–225) is maintained in U.S. Pat. No. 5,914,326. The gluconeogenesis expected by these authors would normally lead to an increase in insulin resistance, an increase in insulin levels and, as a consequence, an increase in the rate of hypertension which is strongly linked to insulin resistance and elevated insulin levels. Hyperinsulinemia is itself a pathological driving force in producing incipient obesity and incipient muscle insulin resistance. (Cusin I, Rohner-Jeanrenaud F, Terrettaz J, Jeanrenaud B. Hyperinsulinemia and its impact on obesity and insulin resistance. Int J Obes Relat Metab Disord. Dec. 16, 1992; Suppl 4:S1–11.) In general, the higher the fasting plasma insulin levels, the more likely the presence of hypertension. (Preuss H G., Burris J F. Adverse metabolic effects of antihypertensive drugs. Implications for treatment. Drug Saf. Jun. 14, 1996; (6):355–64.)
Unknown in the scientific literature is the unusual and surprising ability of HCA to reduce elevated blood pressure. This is a normalizing effect, and there is no evidence nor is there any reason to suspect that the ingestion of HCA will induce low blood pressure in individuals whose blood pressure is already within the normal range. The benefits of HCA in reducing hypertension are especially pronounced in the preferred salt of the acid, potassium hydroxycitrate, and may be further potentiated by the use of a controlled-release form of the compound. Moreover, the authors have found that HCA is a safe hypotensive. Its benefits appear gradually over the course of several weeks and do not seem to be the result of any direct manipulation of nitric oxide production nor of renal function (i.e., diuresis per se is not involved).
The proposed mechanisms by which HCA achieves its hypotensive effect are a reduction in blood insulin levels, a reduction in corticosterone (stress hormone) levels and a long term reduction in the levels of the mineralocorticoids, as well. It is well established that chronic stress leads to chronically elevated levels of glucocorticoids (predominantly cortisol in humans and corticosterone in rodents) and that elevations of aldosterone ultimately follow. The glucocorticoids contribute to insulin resistance by simultaneously promoting both gluconeogenesis (glucose production from noncarbohydrate sources) and lipolysis (the release of free fatty acids) while slowing the oxidation of glucose and sacrificing lean tissue as a source of gluconeogenic precursors, i.e., the chronic elevation of glucocorticoids ultimately is catabolic in its impact upon lean tissues. Elevated blood glucose concentrations are an accepted result of these actions. The compensatory release of mineralocorticoids, such as aldosterone, in response to the chronic elevation of glucocorticoid levels increases sodium retention, and hence blood pressure. All of these factors are known causes of elevated blood pressure.
Quite surprisingly, this effect of HCA has never been mentioned in the literature on the topic. Indeed, those authorities who hold that HCA is gluconeogenic in its actions and primarily useful for increasing ketogenesis typically view it as potentially raising blood sugar levels rather than reducing them and thereby also likely to increase insulin levels. The implied consequence is an increased risk of hypertension. The original pharmaceutical research on HCA performed at Hoffman-La Roche failed to find significant changes in either blood glucose levels or blood insulin levels, undoubtedly in large part due to the fact that almost all of that research used diets which consisted mostly of glucose (e.g., 70% glucose diets were typically employed to encourage lipogenesis). The conclusion of the Roche researchers was that “no significant differences in plasma levels of glucose, insulin, or free fatty acids were detected in (−)-hydroxycitrate-treated rats relative to controls. These data suggest that peripheral metabolism, defined in the present context as metabolite flux, may be involved in appetite regulation . . . ” (Sullivan, Ann C. and Joseph Triscari. Possible interrelationhip between metabolite flux and appetite. In D. Novin, W. Wyriwicka and G. Bray, eds., Hunger: Basic Mechanisms and Clinical Implications (New York: Raven Press,1976) 115–125.)
There is evidence from animal studies, but not from any good human study, that ingested HCA will lower cholesterol blood lipids levels, but much less attention has been paid to free fatty acids. It is known that high levels of circulating free fatty acids are often related to insulin resistance and thereby to elevated blood pressure. Paradoxically for some theories of hypertension, HCA may exercise no effect on or actually increase free fatty acid levels (Ishihara K, Oyaizu S, Onuki K, Lim K, Fushiki T. Chronic (−)-hydroxycitrate administration spares carbohydrate utilization and promotes lipid oxidation during exercise in mice. J Nutr. December 2000; 130(12):2990–5) despite the fact, as the inventors have discovered, that it lowers insulin levels and blood pressure. And, indeed, the issue of blood pressure appears to not be a part of discussions of the effects of HCA. (McCarty M. F. Toward a wholly nutritional therapy for type 2 diabetes. Med Hypotheses March 2000; 54(3):483–487; U.S. Pat. No. 6,113,949; U.S. Pat. No. 5,914,326; U.S. Pat. No. 5,783,603; U.S. Pat. No. 5,626,849.)
Only the potassium and sodium salts of HCA are absorbed well enough to be effective agents at tolerable levels of ingestion. Reasons for this are given in the inventors' copending U.S. Patent Application “Potassium (−)-Hydroxycitric Acid Methods For Pharmaceutical Preparations For Stable And Controlled Delivery.” Derivatives of HCA may also be active and effective in this regard. (U.S. Pat. Nos. 3,993,668; 3,919,254; 3,767,678.) The calcium salt of HCA is extremely widely sold in the United States in dosages ranging up to more than 12 grams per day (providing roughly 6 grams of HCA), and yet there are no reports in the literature of this salt being useful as a hypotensive agent. Liquid forms of HCA currently in use are irritating to the digestive system, depending upon the dose, and may cause distress when used to achieve hypotensive or other purposes. Researchers have found that animals fed high doses of the liquid form of the compound exhibit stress behavior. (Ishihara K, Oyaizu S, Onuki K, Lim K, Fushiki T. Chronic (−)-hydroxycitrate administration spares carbohydrate utilization and promotes lipid oxidation during exercise in mice. J Nutr. December, 2000; 130(12):2990–5.) Similarly, the ethylenediamine salts of HCA used in much of the research performed by Hoffman-La Roche are known to be irritating and even toxic, properties which are due to the ethylenediamine ligand and not to the HCA.
In contrast to the quite limited efficacy found with the calcium salt and some other delivery forms of HCA, the impact of ingestion of appropriate amounts of the appropriate salts of HCA upon subjects with elevated blood pressure has been positive, as has the impact upon insulin levels and corticosterone levels in diets which calorically are not almost exclusively composed of sugars. No prior art suggests this beneficial effect of HCA upon blood pressure, insulin levels or stress hormone levels.